A drainable sight glass assembly and method for installation of such a sight glass on industrial machinery, e.g., oil sumps, oil reservoirs, and diesel fuel tanks, in the art is used to check the condition of oil in a pump or motor housing. In some prior art embodiments, the sight glass can also be used to separate oil and water. Such sight glasses include a top and bottom valve connected to a tubular shaped, transparent sight glass body. In use, oil is drained from the machinery housing into the sight glass through the valve. If water is in the sight glass, then a drain valve located at the bottom of the sight glass can be used to drain the water from the sight glass and thereby drain any water from the machinery housing. In addition, the sight glass can be used as a vessel to transport oil for testing by a laboratory to determine contaminants in the oil that can indicated oil wear.
Unfortunately, contaminants in the motor housing, e.g., dirt, can create a turbulent flow into and a sludge in the sight glass body making it difficult to view the oil for inspection and for water to separate from the oil for draining from the bottom valve. In addition, the creation of a sludge in the sight glass body can, over time, weaken the sight glass body, making the sight glass vulnerable to cracking and shattering. Moreover, if the piping to the sight glass gets clogged, there can be a false indication of oil condition, e.g., the oil in the sight glass can appear clean and pristine contrary to the condition of the oil in the sump. Many industrial applications, therefore, require a maintenance worker to frequently clean and replace the sight glass to prevent any accidental shattering of the sight glass.
The majority of sight glasses in the prior art are either the cylindrical type, discussed above, or used for measuring a level of fluid in a vessel without a means of draining fluid from the sight glass. For example, U.S. Pat. No. 5,406,844 (May et al.) describes drainable sight glass assembly and method for installation of such a sight glass for use in preventing contaminants from entering an injection-molding machine which is similar to the problematic prior art. This sight glass includes a top and bottom valve connects to a tubular shaped, transparent sight glass body, and therefore presents the same problems to the operator as those noted. U.S. Patent Publication 2010/053,786 (Schachinger) describes a drainable sight glass assembly for use in determining the fluid level in a high-pressure container. The sight glass is engaged in an opening in the vessel so that the sight glass forms a plane with the container wall, or alternatively is wedged into the container wall. There are no valves in Schachinger to allow for water to drain from the sight glass, and the pump housing, and accordingly, Schachinger cannot solve the problems noted above. U.S. Pat. No. 4,446,731 (Martin) describes a fluid container, e.g., in a pressurized air filter or lubricator, that has a transparent, angularly shaped, and longitudinally tapered sight glass disposed thereon to allow a user to determine the fluid level in the container. Martin also does not have valves for draining water from the sight glass and housing, and accordingly cannot solve the problems in the art noted above.
What is needed, therefore, is a sight glass that will allow any fluid contaminants in the sight glass to settle towards the bottom to thereby allow an operator to adequately view the material in the sight glass, allow for the separation of oil and water in the sight glass to aid in draining the water therefrom, and allow for the contaminants to be removed when the water is drained from the sight glass.